Nonlinear vibration characteristics of rotor-bearing system with disc-shaft insufficient interference and flexible coupling misalignment fault

For a traditional rotor system, looseness faults caused by disc–shaft insufficient interference are always ignored. Considering disc–shaft looseness caused by insufficient interference, a novel dynamic model of a rotor-bearing system in the presence of coupling misalignment is established in this paper to investigate the characteristics of a disc–shaft looseness fault. Due to the nonlinearity of the contact model between disc and shaft, iterative solution of kinetic equations can be obtained by combining the Newmark- β and Newton–Raphson methods. The vibration characteristics of a rotor-bearing system with and without disc–shaft looseness caused by insufficient interference are compared and analyzed. The results show that a slight collision between disc and shaft can be caused in a disc–shaft early looseness fault, and beat vibration of the systems appears when disc–shaft looseness becomes severe. Considering the effect of coupling misalignment, the vibration responses of a system under different coupling misalignments are further discussed, and parallel misalignment is proved to have a significant effect on disc–shaft looseness. It is expected that these research results will provide a useful reference for the identification and diagnosis of looseness faults caused by disc–shaft insufficient interference.